Slow bubble in radiator reservoir

[Nazz786]

Hi.

Can anyone advice what might be the problem or am I am facing one.

Car: Daihatsu
Model: Sirion
Engine: 1300cc
Type: Liquid cooled
Year: 2011
Mileage: 40,000+ miles
Radiator + Expansion Reservoir Tank system

Symptoms:
There is a slow and steady bubble formation getting into the reservoir/spare radiator tank. Bubble appears after every say 5 seconds.
Please refer to the youtube video link. Although not my car, but it is exactly the same type of issue.

https://www.youtube.com/watch?v=GcYSwHcf89w

Can anyone advice what is happening.

Thanks.

Nazz

 

[TOMJ]

Could be a bad head gasket. Had the same issue with our Civic and it turned out to be a blown head gasket.
Have you changed the coolant recently? if so, air could be trapped in the system.
Have you tried running the engine with the radiator cap off to burp out any air?

Good luck.

 

[Snagglefoot]

You can by a kit at an auto parts store to detect exhaust gas in your coolant caused by a bad head gasket.

 

[BlackBowtie63]

As stated above, air in your system or a bad head gasket.

 

[Nazz786]

Hi all,

Thanks for the reply. I hope its not a blown head gasket.

About two months back the coolant was changed. All seemed alright till about last week.

I always mark the coolant reservoir tank level with a sharpie.

However a couple days back I noticed the level on the reservoir dropped quite a bit.

I checked all hoses and nothing was leaking. No idea where it went.

So I marked the new lower level on the reservoir with a sharpie.
I've been keeping a eye on it for the last couple of days but the level hasn't dropped any further.

So there you go, sudden missing coolant and now its bubbles ever so slowly, one bubble at a time.

Not sure whats going on.

 

[anndel]

If you recently drained/refill the coolant, could be trapped air bubbles still in the system.
Check your dipstick and beneath the oil filler cap, any milkshake?
Get a leak detector like Snagglefoot mentioned. It tests for gas in the coolant and turns color if it head gasket is leaking.

Good luck

 

[Nazz786]

Thanks for the suggestion. Will try to burp out.

*Checked the dipstick and cap - No signs of any milkshake residue.

 

[FCD]

The only time i have seen bubbling in the coolant expansion tank on my 1988 Escort is when i changed the coolant, just the air that inevitably enters the system escaping.
However i only saw it on the first start after changing the coolant.